Endogenous nitrogen metabolism in Oncorhynchus kisutch
Date
1973
Authors
Anderson, Maria Margareta
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Abstract
Reviews are presented of the pertinent literature dealing with endogenous nitrogen metabolism in both mammals and fish. In addition, the endogenous nitrogen excretion of the coho salmon, Oncorhynchus kisutch was investigated. Ammonia is believed to constitute the major nitrogenous waste product of fish. Therefore, the rate of ammonia nitrogen excretion by individual fasting fish in distilled water was quantified. The rate of elimination was found to increase with a rise in ambient temperature from five to twenty degrees Celsius. However the results obtained were exaggerated in magnitude. As an alternative procedure, the body composition of fingerling salmon was analysed during a ten week fast. Endogenous nitrogen was then correlated to the rate of protein oxidation and to heat production. The latter was determined from the rates of both protein and fat catabolism. A tentative value for endogenous excretion was determined - 23 milligrams nitrogen per kilogram fish per day. The ratio of rate of endogenous nitrogen excretion to calculated metabolic rate was estimated to be 2.3 milligrams excreted nitrogen per kilocalorie.